In an in-line moulding installation, shoulders are positioned through apertures in the bases of the moulds so that the shoulder stems project upwardly and the portions of the shoulders, which will, in use, accept the rail retaining clips, depend from the moulds (the sleepers being moulded upside down), reinforcing wires are run along the length of the line of moulds and are tensioned, the concrete is poured to embody the upstanding shoulder stems, the concrete is allowed to at least partly cure and spacers between adjacent sets of moulds are withdrawn, and after sufficient additional curing has taken place, the reinforcing wires are severed between the sleepers of adjacent moulds. The moulds are then inverted, and the completed sleepers discharged onto a fork-lift truck or other handling means.
One difficulty which is encountered with certain types of shoulders is that they must be accurately located, and to this end the apertures in the mould bases must be a close enough fit for the shoulders that there is little movement. If the clearance space between the shoulder edges and the walls defining the apertures is too small, removal of the moulded sleepers from the moulds is rendered difficult, while if they are too large, there is a flow-through of slurry from the concrete mix and this will deposit upon locating means and retention means carried beneath the sleeper moulds, and if this occurs a great deal of time needs to be spent in maintenance and cleaning between pours of concrete in the installation.
This invention is particularly directed to use with a concrete sleeper shoulder of the type having a stem to be embodied within the concrete, and an upwardly directed recess defined by a front (datum) wall and side wings, and wherein the side wings contain wing side recesses which face one another. Such shoulders are known in the art and will accept plate-like clips.